Allowing big regional cities like Birmingham to decline while wealth and power was concentrated in London has helped cause Britain’s economic difficulties, David Cameron has claimed.

The Conservative leader said a “balanced economy”, in which wealth was spread more evenly, would be better placed to cope with the global downturn.

But he warned that Birmingham, which had once been an “economic powerhouse”, had slipped well behind similar European cities.

Mr Cameron said his party would published detailed plans for devolving power away from the capital to local councils across the country, as he spoke to regional journalists in London.

He highlighted Conservative proposals for a £20 billion high speed rail line, linking Birmingham, Manchester, Leeds and London, saying it would make major regional cities more attractive places to do business.

Many of the comments will be welcomed by Birmingham City Council, which has set out plans to seize control of local health and police services which are currently accountable to central government departments in Whitehall.

But Mr Cameron also reiterated his support for directly-elected city mayors, a policy which is opposed by Mike Whitby, Birmingham Council’s Tory leader.

He said: “A more localised economy, in which every part of the country is economically active, is a more resilient economy.

“Let’s be frank - growth has been too concentrated in London and other areas of the South East, and it not really surprising that wealth is concentrated there when power is concentrated there too.

“So when London sneezes in the night, the whole country catches a cold.”

Other parts of the country had been left behind, he said.

“A century ago, Birmingham, Manchester, Liverpool and Newcastle were the economic powerhouses of the world.

“Now, they only have half the GDP per head of other major European cities. After London, the next English city in the European league table of economic performance is actually Bristol, in 34rd place.”

Better transport links would help Britain’s big cities to succeed, he said.